openvswitch: remove support for legacy tunnel types

ovs-vswitchd doesn't use OVS_VPORT_TYPE_GRE/VXLAN/GENEVE with the
Linux kernel module since adding support for standard tunnel devices
with COLLECT_METADATA back in 2017.  The code to use them was only
activated as a fallback for old kernels, so not used in practice.  And
it is now fully removed in the upcoming OVS 4.0 release.

Modern way to use tunnels with OVS is to create standard tunnel ports
with RTM_NEWLINK + COLLECT_METADATA and add them as OVS_VPORT_TYPE_NETDEV.

Device reference management and the netlink options parsing for these
legacy port types is complicated and was a CVE magnet in the previous
release cycles.  Existence of these modules also makes locking analysis
for geneve module and other core tunnel devices unnecessarily more
complicated, especially in light of migration to per-netns locking.

Since there are no actual users for these port types for a very long
time, let's just remove the support entirely.  There is no practical
reason to run OVS from 2017 on a recent kernel.

While it's technically a uAPI change in some sense, from the user's
perspective this removal looks indistinguishable from the kernel built
with CONFIG_OPENVSWITCH_GENEVE/VXLAN/GRE disabled.  And it seems like
removal of unused drivers/modules is not a rare event these days.

A comment is added to the uAPI header noting that standard RTM_NEWLINK
with COLLECT_METADATA followed by OVS_VPORT_CMD_NEW with the simple
OVS_VPORT_TYPE_NETDEV should be used instead.

Modules responsible for these tunnel ports are removed as well as
selftests covering this functionality.  Further cleanups will follow.

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Link: https://patch.msgid.link/20260804182049.2289754-2-i.maximets@ovn.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 26 insertions, 5 deletions

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index aa2acdbda8f8..440825e65837 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -244,13 +244,33 @@ enum ovs_vport_cmd {
 	OVS_VPORT_CMD_SET
 };
 
+/**
+ * enum ovs_vport_type - OVS vport types for %OVS_VPORT_ATTR_TYPE.
+ * @OVS_VPORT_TYPE_NETDEV: Existing network device attached as a vport.
+ * @OVS_VPORT_TYPE_INTERNAL: Network device implemented by the OVS datapath.
+ * @OVS_VPORT_TYPE_GRE: Legacy GRE tunnel.  Not supported, see below.
+ * @OVS_VPORT_TYPE_VXLAN: Legacy VXLAN tunnel.  Not supported, see below.
+ * @OVS_VPORT_TYPE_GENEVE: Legacy Geneve tunnel.  Not supported, see below.
+ *
+ * The tunnel vport types are not supported.  Instead, create the tunnel device
+ * using %RTM_NEWLINK with the appropriate %IFLA_INFO_KIND (e.g. ``gre``,
+ * ``gretap``, ``vxlan``, ``geneve``, or other tunnel types) and add it as
+ * %OVS_VPORT_TYPE_NETDEV.  To match and set tunnel parameters on a per-flow
+ * basis, the tunnel device should collect metadata.  To do that, some tunnel
+ * types require an explicit flag such as %IFLA_VXLAN_COLLECT_METADATA for
+ * ``vxlan``, while others such as ``bareudp`` collect metadata
+ * unconditionally.
+ */
 enum ovs_vport_type {
+	/* private: */
 	OVS_VPORT_TYPE_UNSPEC,
+	/* public: */
 	OVS_VPORT_TYPE_NETDEV,   /* network device */
 	OVS_VPORT_TYPE_INTERNAL, /* network device implemented by datapath */
-	OVS_VPORT_TYPE_GRE,      /* GRE tunnel. */
-	OVS_VPORT_TYPE_VXLAN,	 /* VXLAN tunnel. */
-	OVS_VPORT_TYPE_GENEVE,	 /* Geneve tunnel. */
+	OVS_VPORT_TYPE_GRE,      /* GRE tunnel (legacy, not supported). */
+	OVS_VPORT_TYPE_VXLAN,	 /* VXLAN tunnel (legacy, not supported). */
+	OVS_VPORT_TYPE_GENEVE,	 /* Geneve tunnel (legacy, not supported). */
+	/* private: */
 	__OVS_VPORT_TYPE_MAX
 };
 
@@ -284,7 +304,7 @@ enum ovs_vport_type {
  * %OVS_VPORT_ATTR_NAME attributes are required.  %OVS_VPORT_ATTR_PORT_NO is
  * optional; if not specified a free port number is automatically selected.
  * Whether %OVS_VPORT_ATTR_OPTIONS is required or optional depends on the type
- * of vport.
+ * of vport.  None of currently supported vport types support options.
  *
  * For other requests, if %OVS_VPORT_ATTR_NAME is specified then it is used to
  * look up the vport to operate on; otherwise dp_idx from the &struct
@@ -336,7 +356,8 @@ enum {
 #define OVS_VXLAN_EXT_MAX (__OVS_VXLAN_EXT_MAX - 1)
 
 
-/* OVS_VPORT_ATTR_OPTIONS attributes for tunnels.
+/* OVS_VPORT_ATTR_OPTIONS attributes for legacy tunnel vports.
+ * Not supported, see the note for enum ovs_vport_type.
  */
 enum {
 	OVS_TUNNEL_ATTR_UNSPEC,